LED array member and integrated control module assembly with built-in switching converter

ABSTRACT

A LAM/ICM assembly comprises an integrated control module (ICM) and an LED array member (LAM). The ICM includes interconnect through which power from outside the assembly is received. In a first novel aspect, active circuitry is embedded in the ICM. In one example, the circuitry monitors LED operation, controls and supplies power to the LEDs, and communicates information into and out of the assembly. In a second novel aspect, a lighting system comprises an AC-to-DC converter and a LAM/ICM assembly. The AC-to-DC converter outputs a substantially constant current or voltage. The magnitude of the current or voltage is adjusted by a signal output from the LAM/ICM. In a third novel aspect, the ICM includes a built-in switching DC-to-DC converter. An AC-to-DC power supply supplies a roughly regulated supply voltage. The switching converter within the LAM/ICM receives the roughly regulated voltage and supplies a regulated LED drive current to its LEDs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority under 35U.S.C. §120 from, nonprovisional U.S. patent application Ser. No.14/614,361 entitled “LED Array Member and Integrated Control ModuleAssembly with Built-In Switching Converter,” filed on Feb. 4, 2015, nowU.S. Pat. No. 9,351,358. application Ser. No. 14/614,361, in turn, is acontinuation of, and claims priority under 35 U.S.C. §120 from,nonprovisional U.S. patent application Ser. No. 14/062,079 entitled “LEDArray Member and Integrated Control Module Assembly with Built-InSwitching Converter,” filed on Oct. 24, 2013, now U.S. Pat. No.8,975,821. application Ser. No. 14/062,079, in turn, claims priorityunder 35 U.S.C. §119 from U.S. Provisional Application No. 61/856,552,entitled “LED Array Member and Integrated Control Module Assembly,”filed on Jul. 19, 2013. The subject matter of each of the foregoingdocuments is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to packaging of light-emittingdiodes.

BACKGROUND INFORMATION

A light emitting diode (LED) is a solid state device that convertselectrical energy to light. Light is emitted from active layers ofsemiconductor material sandwiched between oppositely doped layers when avoltage is applied across the doped layers. In order to use an LED chip,the chip is typically enclosed along with other LED chips in a package.In one example, the packaged device is referred to as an LED array. TheLED array includes an array of LED chips mounted onto a heat conductingsubstrate. A layer of silicone in which phosphor particles is embeddedis typically disposed over the LED chips. Electrical contact pads areprovided for supplying current into the LED array and through the LEDchips so that the LED chips can be made to emit light. Light emittedfrom the LED chips is absorbed by the phosphor particles, and isre-emitted by the phosphor particles so that the re-emitted light has awider band of wavelengths. Making a light fixture or a “luminaire” outof such an LED array, however, typically involves other components. TheLED array generates heat when used. If the temperature of the LED arrayis allowed to get too high, performance of the LED array may suffer andthe LED array may actually fail. In order to remove enough heat from theLED array so as to keep the LED array adequately cool, the LED array istypically fixed in some way to a heat sink. In addition, power mustsomehow be supplied to the LED array. Power supply circuitry istypically required to supply current to the LED array in a desired andsuitable fashion. Optical components are also generally employed todirect and focus the emitted light in a desired fashion. There are manyconsiderations involved in packaging an LED array so that it the arraycan be used effectively in an overall luminaire. Ways of packaging LEDarrays for use in luminaires are sought.

SUMMARY

An LAM/ICM assembly comprises an integrated control module (ICM) and anLED array member (LAM). In one example, the ICM is a thick,washer-shaped, molded plastic member that fits over an upper surface ofthe LAM and holds the LAM so that a bottom surface of the LAM is held ingood thermal contact against a heat sink. The ICM has holes throughwhich threaded screws or bolts can extend. The screws or bolts extendthrough the holes in the ICM and engage corresponding threaded holes inthe heat sink, thereby pulling the washer-shaped ICM toward the heatsink. The ICM in turn presses downward on the top of the LAM and causesthe bottom surface of the LAM to be pressed against the heat sink.

In addition, the ICM includes terminals and an interconnect layerthrough which power from outside the assembly is received onto theassembly and is supplied through the ICM, and through mating sets ofcontact pads of the ICM and LAM, and to the LAM so that the LEDs of theLAM can be powered and emit light. The ICM does not cover the LEDs ofthe LAM, but rather a central circular opening in the washer-shaped ICMallows light emitted from the LEDs to pass upward through the centralopening and away from the heat sink.

In accordance with a first novel aspect, the washer-shaped ICM includescircuitry involving active electronic components. The circuitry monitorsLAM operation, controls and supplies power to the LAM, and communicatesinformation into and out of the assembly. In one example, the circuitrymonitors the voltage disposed across a string of LEDs of the LAM,monitors the current flowing through the string of LEDs of the LAM, andmonitors the temperature of the LED array. In one example, the ICMincludes a printed circuit board to which this circuitry is mounted. Thecircuitry and the printed circuit board are encapsulated in injectionmolded plastic. Injection molded plastic overmolds almost all of theprinted circuit board including the periphery of the printed circuitboard, the upper surface of the printed circuit board, and the lowersurface of the printed circuit board. There are, however, exposedcontacts on the bottom of the printed circuit board that extend aroundin the bottom of the inside lip of the central opening in the ICM. Whenthe LAM is fitted up into place into the central opening in the ICM, LAMcontact pads on the peripheral edge of upper surface of the LAM makeelectrical contact with corresponding ICM contact pads on the bottom ofthe inside lip of the ICM. Power is supplied through the ICM and to theLAM through these contacts, and LAM operation is monitored by the ICMthrough these contacts.

In accordance with a second novel aspect, a lighting system comprises anAC-to-DC converter and a LAM/ICM assembly, where the LAM/ICM supplies acontrol signal back to the AC-to-DC converter. The AC-to-DC converterreceives a supply voltage from an AC voltage source, such as a 110 VACvoltage source. The AC-to-DC converter outputs a substantially constantand regulated current or voltage, where the substantially constantcurrent or voltage has an adjustable magnitude. The level to which thecurrent or voltage is regulated can be changed by appropriate control ofthe control signal (for example, a zero volts to ten-volt control inputsignal) to the AC-to-DC converter. If the ICM determines that more powershould be received, then the ICM increases the level of the zero to tenvolt control signal. If the ICM determines that less power should bereceived, then the ICM decreases the level of the zero-to-ten-voltcontrol signal. The AC-to-DC converter responds by increasing ordecreasing the current or voltage level to which it regulates, asinstructed by the control signal.

In the case where the adjustable AC-to-DC converter outputs a regulatedconstant current, a FET of the LAM/ICM assembly simply turns on or offcurrent flow through the LAM. If LAM current flow is on, then themagnitude of the current flowing from the AC-to-DC converter isdetermined by the feedback zero volts to ten-volt control signal thatthe LAM/ICM supplies back to the AC-to-DC converter. Since the AC-to-DCconverter output cannot normally be turned fully off by the zero to 10volt control signal, and because the circuitry of the ICM requires asupply voltage at all times to operate, the ICM includes a semiconductorswitch that is operable in the saturated mode as an “on-off” switch tothe LAM. The ICM also includes circuitry that controls the semiconductorswitch so that when it is desired to have the LAM produce no lightwhatsoever, the switch is turned “off” interrupting all current flow tothe LAM, but leaving voltage output from the AC-to-DC converter at theICM which can be used to continue to power the circuitry of the ICMwhile the LAM is “off”.

In the case where the adjustable AC-to-DC converter outputs a regulatedconstant voltage, the ICM of the LAM/ICM assembly receives power fromthe AC-to-DC converter and supplies power the LEDs of the LAM. The ICMincludes a semiconductor switch that is operable in the linear mode. TheICM also includes circuitry that controls the semiconductor switch inthe linear mode such that the ICM receives the substantially constantvoltage from the AC-to-DC converter and causes a controlled DC currentto flow through the LAM. Linear operation of the semiconductor switch iscontrolled to fine tune the magnitude of the DC current flowing throughthe LEDs. The circuitry also outputs a control signal that is suppliedout of the LAM/ICM assembly and back to the AC-to-DC converter. Thiscontrol signal is the zero-volt to ten-volt control input signal thatcontrols the AC-to-DC converter. Using this control signal, thecircuitry of the LAM/ICM assembly controls the AC-to-DC converter sothat the LED voltage at which the LEDs of the LAM are driven is close to(for example, within ten percent of) the voltage at which the constantcurrent is supplied by the AC-to-DC converter to the LAM/ICM assembly.Because the voltages are close, power dissipation of the semiconductorswitch in the ICM is low enough that it can perform its regulatingfunction without overheating. In one example, the semiconductor switchis disposed in a semiconductor package, where the semiconductor packageof the switch extends from a bottom surface of the ICM and is a goodthermal contact with the heat sink.

In accordance with a third novel aspect, a lighting system comprises anAC-to-DC converter and a LAM/ICM assembly. The AC-to-DC converterreceives a supply voltage from an AC voltage source, such as a 110 VACvoltage source. The AC-to-DC converter in the third novel aspect outputsa substantially constant voltage. The ICM of the LAM/ICM assemblyincludes a switching DC-to-DC converter. The switching DC-to-DCconverter of the ICM receives the substantially constant DC voltage fromthe AC-to-DC converter and supplies a substantially constant andregulated LED DC drive current to the LAM.

The switching DC-to-DC converter that is embedded in the ICM may be astep down converter whose input voltage is higher than its outputvoltage, or the switching DC-to-DC converter that is embedded in ICM maybe a step up converter whose input voltage is lower than its outputvoltage, or the switching DC-to-DC converter that is embedded in the ICMmay be a combination converter whose incoming input voltage can behigher or lower than the converter output voltage. In one specificexample, the switching DC-to-DC converter of the ICM is a step-down buckconverter that is switched at about 10 MHz. In other examples, theswitching DC-to-DC converter of the ICM is one of a step-up boostconverter, a SEPIC converter, and a boost/buck combination converteroperating at switching frequencies that may be substantially higher than10 MHz to keep the physical size of electronic components small.

In one example, the LAM includes a plurality of strings of LEDs. The ICMincludes a plurality of buck converters, where all the buck convertersare controlled by a common microcontroller that is a part of the ICM.Each string of LEDs is supplied with an independently controlled LEDdrive current by a corresponding one of the plurality of buckconverters. In some embodiments, multiple such LAM/ICM assemblies aredriven in parallel by the same AC-to-DC converter, where the AC-to-DCconverter outputs only a roughly regulated constant voltage. Within eachLAM/ICM, the microcontroller monitors the voltage supplied to each LEDstring, monitors the current flowing through each LED string, andmonitors the temperature of the LED array. The microcontroller controlsthe current supplied to each string independently of the currentssupplied to the other strings. The microcontroller may control thecurrent supplied to each string of LEDs by controlling the switchingDC-to-DC converter or converters of the ICM that supply the drivecurrents to the strings of LEDs. In some examples, the ICM includes anRF (Radio Frequency) transceiver that the microcontroller uses tocommunicate information to and from other RF transceivers locatedoutside the LAM/ICM assembly. The ICM also includes a terminal throughwhich the microcontroller can communicate digital information into andout of the LAM/ICM assembly. The communication interface can be a wiredone through this terminal, or the communication interface can be awireless one provided by the RF communication link.

Further details and embodiments and techniques are described in thedetailed description below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 is a perspective view of the connector side of the top of an LEDarray member (LAM)/integrated control module (ICM) assembly.

FIG. 2 is a perspective view of the top of an LED array member(LAM)/integrated control module (ICM) assembly from the side oppositethe connector.

FIG. 3 is a perspective view of the bottom of the LAM/ICM of FIGS. 1 and2.

FIG. 4 is a cross-sectional, top-down view of the LAM/ICM assembly ofFIGS. 1 and 2.

FIG. 5 is top-down view of one example of a LAM usable with the ICM ofFIGS. 1 and 2.

FIG. 6 is cross-sectional view showing how the LAM fits up and into thecentral opening in the ICM.

FIG. 7 is a diagram showing one example of an ICM contact pad disposedon the inside lip of the ICM.

FIG. 8 is a more detailed diagram showing how a LAM contact pad on theperipheral edge of upper surface of the LAM makes contact with acorresponding ICM contact pad in the bottom of the inside lip of theICM.

FIG. 9 is a cross-sectional view taken along line A-A′ of the LAM/ICM ofFIG. 4.

FIG. 10 is a cross-sectional view taken along line B-B′ of the LAM/ICMof FIG. 4.

FIG. 11 is a cross-sectional view taken along line C-C′ of the LAM/ICMof FIG. 4.

FIG. 12 is a cross-sectional view taken along line D-D′ of the LAM/ICMof FIG. 4.

FIG. 13 is a circuit diagram of the LAM/ICM assembly in accordance witha second novel aspect, in an example in which the AC-to-DC converteroutputs a regulated constant current and the AC-to-DC converter receivesa control signal back from the LAM/ICM assembly.

FIG. 14 is a diagram of a lighting system that includes the LAM/ICMassembly of FIG. 13.

FIG. 15 is a circuit diagram of the LAM/ICM assembly in accordance withthe second novel aspect, in an example in which the AC-to-DC converteroutputs a regulated constant voltage.

FIG. 16 is a top-down diagram of another example of a LAM that can beused with the ICM of FIGS. 1 and 2.

FIG. 17 is a circuit diagram of the LAM/ICM assembly in accordance witha third novel aspect.

FIG. 18 is a circuit diagram of a buck converter suitable for use in theLAM/ICM assembly of FIG. 17.

FIG. 19 is a table that sets forth parameters and componentscharacteristics of the buck converter of FIG. 18.

FIG. 20 is a diagram illustrating a first way to drive multiple LEDstrings with multiple buck converters, where the multiple buckconverters are parts of the ICM.

FIG. 21 is a diagram illustrating a second way to drive multiple LEDstrings with multiple buck converters, where the multiple buckconverters are parts of the ICM.

FIG. 22 is a diagram of a lighting system that includes the LAM/ICMassembly of FIG. 17.

DETAILED DESCRIPTION

Reference will now be made in detail to background examples and someembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

FIG. 1 is a perspective view of the top of an LED assemblymember/integrated control module assembly (LAM/ICM assembly) 1. Thereare two parts of the LAM/ICM assembly: a LED assembly member 2 (FIG. 3)and an integrated control module 3. The LED assembly member 2 ishereinafter referred to as the LAM. The integrated control module 3 ishereinafter referred to as the ICM. As illustrated in the diagram, theLAM/ICM assembly 1 is a disk-shaped structure that has a circular upperouter peripheral edge 4. Reference numeral 5 identifies the uppersurface of the LAM/ICM assembly 1. The upper surface 5 is a surface of amolded plastic encapsulant 40 (FIG. 6). Two sets of two holes 6-9 areprovided through which threaded screws or bolts (not shown) can extendto fix the LAM/ICM assembly 1 to a heat sink. The disk-shaped shadedobject in the center in the illustration is a disk-shaped amount ofsilicone 11. The silicone 11 has phosphor particles embedded in it. Thissilicone with the embedded phosphor particles overlies an array of lightemitting diodes (LEDs). The LEDs are not seen in the diagram becausethey are disposed under the silicone. The LAM/ICM assembly 1 furtherincludes a header socket 12 and ten header pins, such as pins 13, 14, 15and 16. Pin 13 is a power terminal through which a supply voltage or asupply current is received into the LAM/ICM assembly 1. Pin 14 is apower terminal through which the current returns and passes out of theLAM/ICM assembly. Pin 14 is a ground terminal with respect to the powerterminal 13. Pin 15 is a data signal terminal through which digitalsignals are communicated into and/or out of the LAM/ICM assembly. Pin 16is a signal ground for the data signals communicated on pin 15. Theillustrated example of the LAM/ICM assembly that has ten header pins isbut one example. In other examples, fewer or more header pins areprovided in the header socket 12, and assignment of power or signals tothe pins can be on different positions than illustrated herein. If theLEDs underneath silicone 11 are powered and emitting light, then thelight passes upward through the central circular opening 17 in uppersurface 5, and is transmitted upward and away from the LAM/ICM assembly1.

FIG. 2 is a perspective view of the top of the LAM/ICM assembly, takenfrom the other side of the LAM/ICM assembly opposite header socket 12.

FIG. 3 is a perspective view of the bottom of the LAM/ICM assembly 1.Reference numeral 18 identifies the circular lower outer peripheral edgeof the LAM ICM assembly. Whereas the shape of central opening 17 at theupper surface 5 of the ICM is circular as pictured in FIG. 1, the shapeof the central opening 17 at the bottom surface 19 of the ICM aspictured in FIG. 3 is square. The LAM 2 is disposed in the centralopening 17 so that the bottom surface 20 of the LAM 2 protrudes justslightly from the plane of the bottom surface 19 of the ICM 3. From theperspective of the illustration of FIG. 3, the bottom surface 20 of theLAM is slightly higher than is the bottom surface 19 of the ICM. Thebottom surface 20 of the LAM is actually the bottom surface of asubstrate member 57 of the LAM (FIG. 6).

FIG. 4 is a cross-sectional, top-down diagram of the LAM/ICM assembly 1.The round circle identified by reference numeral 17A is the edge ofcircular central opening 17 at the upper surface of the ICM. The dashedsquare identified by reference numeral 17B is the edge of thesquare-shaped central opening 17 at the bottom surface of the ICM. Thefour dashed squares 21-24 identify where four LED dice are disposedunderneath the silicone 11.

FIG. 5 is a simplified top-down diagram of one example of LAM 2, wherethe silicone and solder mask layers are not shown so that themetallization patterns of die attachment of LED dice 21-24 can be seen.There are five areas of metal 25-29 disposed on an insulative layer 30,where the insulative layer 30 in turn is disposed on the substratemember 57. The insulative layer 30 insulates each of the metal areasfrom the substrate member 57 of the LAM. The substrate member 57 in thiscase is a square piece of aluminum sheet. The four LED dice 21-24 arelateral LED dice that are die-attached to the central metal area 29. TheLED dice are wire bonded to form two parallel strings. An LED drivecurrent can flow through the first string by flowing from metal area 25,through LED die 21, through LED die 23, and to metal area 28. An LEDdrive current can flow through the second string by flowing from metalarea 25, through LED die 22, through LED die 24, and to metal area 28.Reference numeral 31 identifies one of the bond wires. In addition toLED dice 21-24, LAM 2 includes a temperature sensing GaN diode die 32.In one example, this GaN diode die 32 is of identical construction tothe LED dice. In the illustrated example, it is of identicalconstruction except for the fact that it is a smaller die. The anode ofGaN diode 32 is coupled via a bond wire to metal area 26. The cathode ofGaN diode 32 is coupled via another bond wire to metal area 27. Thedashed line 33 identifies the circular outer periphery of a rim 34 thatretains the silicone 11. As can be seen from FIGS. 1, 2 and 4, this rim34 is of a diameter that is just smaller than the inside diameter of thecentral opening 17 in the upper surface of the ICM. The outwardlyextending portions of the metal areas at the corners of the LAM of FIG.5 are referred to as LAM contact pads because these areas of metal areexposed, and are not covered with soldermask. Reference numerals 35-38identify these LAM contact pads in the illustration of FIG. 5.

FIG. 6 is a cross-sectional diagram that shows how the LAM 2 fits upinto the central opening 17 in the ICM 3. ICM 3 includes an interconnectstructure 39, a plurality of electronic components that are mounted tothe interconnect structure, and the amount of insulative molded plasticencapsulant 40 that encases and encapsulates the interconnect structureand the electronic components. In the illustrated example, theinterconnect structure 39 is a multi-layer printed circuit board (PCB).One of the electronic components 41 of the circuitry is seen incross-section as a rectangle. Not all of the printed circuit board isactually encapsulated, but rather the bottom of the inside lip 42 of thecentral opening 17 is not covered with encapsulant so that portions ofmetallization on this lip 42 can serve as ICM contact pads. Each of theLAM contact pads on the top of the LAM 2 is soldered to correspondingone of the ICM contact pads on the downward facing inside lip 42 of theICM. In this example, amounts 43 and 44 of solder paste are disposed onthe LAM contact pads, and the LAM 2 is moved up and into contact withthe ICM 3, and then the assembly is heated in a reflow soldering processto solder the LAM contact pads to the ICM contact pads. Other solderingand mechanical/electrical interface methods such as conductive adhesivescould be used instead of reflow soldering with solder paste as describedherein.

FIG. 7 is a view of the bottom of the ICM 3. Metal traces of the printedcircuit board 39 extend to the inside lip 42 and connect to ICM contactpads through conductive vias. For example, trace 45 contacts ICM contactpad 46 through conductive via 47. Trace 48 contacts ICM contact pad 49through conductive via 50.

FIG. 8 is a view that shows how LAM contact pad 36 is coupled via solder44 to the corresponding ICM contact pad 46 on the inside lip of the ICM.The PCB 39 includes three metal layers 51, 52 and 53 and threefiberglass layers 54, 55 and 56. The substrate member 57 of the LAM 2 iscovered by insulative layer 30. Electrical contact is made from metalarea 26, a part of which is LAM contact pad 36, up through solder 44, toICM contact pad 46, and through a conductive via in the PCB, and tometal interconnect layer 51 of the PCB 39. The interconnect structuredescribed herein is that of a conventional FR-4 PCB; however, otherstructures such as Kapton “flex circuit” or metal clad PCB circuits canalso be used for this interconnect structure.

FIG. 9 is a cross-sectional view of the LAM/ICM assembly 1 of FIG. 4taken along sectional line A-A′ (shown on a heat sink 60). Bolts 58 and59 extend through holes 6-7, and hold the bottom surface 20 of LAM 2 ingood thermal contact with the heat sink 60 through a layer 61 of athermal interface material (TIM). There are no LAM contact pads or ICMcontact pads in the cross-section illustrated. Reference numerals 62 and63 identify additional electronic components of the circuitry mounted onPCB 39. The circuitry is overmolded by the injection molded plasticencapsulant 40.

FIG. 10 is a cross-sectional view of the LAM/ICM assembly 1 of FIG. 4taken along sectional line B-B′ (shown on a heat sink). Solder 43couples LAM contact pad 37 to ICM contact pad 64. Solder 44 couples LAMcontact pad 36 to ICM contact pad 46.

FIG. 11 is a cross-sectional view of the LAM/ICM assembly 1 of FIG. 4taken along sectional line C-C′ (shown on heat sink 60). Electroniccomponents of the circuit as seen in cross-section include acommunication integrated circuit 65, a microcontroller integratedcircuit 66, and a FET switch 67. Each of these three components is apackaged device that is in turn overmolded by the plastic encapsulant 40of the ICM. In the case of the FET switch 67, a surface of the packageforms a part of the bottom surface of the ICM so that when the ICM ispressed against the heat sink 60 (with the TIM 61 in between), thebottom surface of the FET switch package makes good thermal contact withthe heat sink 60. The FET switch package may, for example, be aDCB-isolated SMPD (direct copper bonded isolated surface mount powerdevice) package whose downward facing surface is a heat-dissipatingsubstrate that is intended to be pressed against a heat sink.

FIG. 12 is a cross-sectional view of the LAM/ICM assembly 1 of FIG. 4taken along sectional line D-D′ (shown on a heat sink).

FIG. 13 is a diagram of the LAM/ICM assembly 1 in accordance with asecond novel aspect. The LAM/ICM assembly 1 is illustrated with the heatsink 60 and with optics 68 denoted as blocks. The microcontroller 66monitors the temperature of the LAM 2 via a temperature interfacecircuit 69. Temperature interface circuit 69 includes a constant currentsource that supplies a constant current 70 to the temperature sensingGaN die 32 via ICM contact pad 46, LAM contact pad 36, LAM contact pad38 and ICM contact pad 49. The temperature interface circuit 69 alsoincludes a voltage amplifier that amplifies the sensed voltage acrossLAM contact pads 36 and 38 and supplies the resulting amplified voltagesignal T 72 to the microcontroller 66 via conductor 73. In addition,microcontroller 66 monitors the voltage V with which the LEDs of LAM 2are driven. This LED drive voltage is the voltage between LAM contactpads 35 and 37. A current and voltage measuring interface circuit 78measures this voltage via conductors 79 and 80. In addition,microcontroller 66 monitors the LED drive current 74 flowing through theLEDs of the LAM 2. This current 74 flows from pin 13, through ICMcontact pad 75, through LAM contact pad 35, through the LEDs, throughLAM contact pad 37, through ICM contact pad 64, through current senseresistor 77, through FET switch 67, out of the LAM/ICM assembly via pin14. The current and voltage measuring interface circuit 78 detects theLED drive current 74 as the voltage dropped across the current senseresistor 77. This voltage is detected across conductors 80 and 81. Thevoltage and current measuring interface circuit 78 receives the voltagesense and current sense signals, low pass filters them, amplifies them,and performs level shifting and scaling to generate a voltage sensesignal V 82 and a current sense signal I 83. The voltage and currentsense signals 82 and 83 are supplied to the microcontroller 66 viaconductors 84 and 85, respectively.

The T signal 72, the V signal 82, and the I signal 83 are converted intodigital values by the analog-to-digital converter (ADC) 86 of themicrocontroller. A main control unit (MCU) 87 of the microcontrollerexecutes a program 71 of processor-executable instructions. The I, V andT signals, as well as information received from communication integratedcircuit 65, are used by the MCU 87 to determine how to control FETswitch 67. In the present example, the MCU 87 can control the FET switchto be nonconductive, thereby turning off the LEDs. The MCU 87 cancontrol the FET switch to be fully conductive, thereby turning on theLEDs to a brightness proportional to the current supplied by the AC-DCconverter as controlled by the zero to ten volt signal also produced bythe MCU as directed by the control program. As explained in furtherdetail below, the ICM 3 receives a substantially constant current viapins 13 and 14 from an AC-to-DC power supply circuit 88 (see FIG. 14).The AC-to-DC power supply circuit 88 has a constant current output, themagnitude of the constant current being controllable by a zero to tenvolt signal received by the AC-to-DC power supply circuit. The voltagethat results across pins 13 and 14 when this constant current is beingsupplied to the LAM/ICM assembly 1 is about 50 volts. Themicrocontroller 66 controls the FET switch 67 to be fully on with nearlyzero voltage across it when the LAM is to be illuminated. To accomplishcontrol for a desired LED brightness (desired amount of current flowthrough the LEDs of the LAM), the microcontroller 66 sends a zero to tenvoltage dimming control signal 89 back to the AC-to-DC power supplycircuit 88 via conductor 90, and data terminal 15. The microcontroller66 uses this control signal 89 to increase and to decrease the magnitudeof the constant current 74 being output by the AC-to-DC power supplycircuit 88. The circuit components 69, 78, 66 and 65 are powered from alow DC supply voltage such as 3 volts DC. A component voltage supplycircuit 91 generates this 3 volt supply voltage from the 50 volts acrosspins 13 and 14. The 3 volt supply voltage is supplied onto voltagesupply conductor 90. Conductor 93 is the ground reference conductor forthe component supply voltage. Because only a small amount of power isrequired to power the circuitry embedded in the ICM, the componentvoltage supply circuit 91 may be a simple linear voltage regulator.

FIG. 14 is a system level diagram of a lighting system 94. Lightingsystem 94 includes the power supply circuit 88, the LAM/ICM assembly 1,and internet connectivity circuitry 95. The LEDs of the LAM can bemonitored and controlled remotely by communicating across the internet96. Information can be communicated from the internet 96, across anethernet connection 97, through the internet connectivity circuitry 95,from antenna 98 of the internet connectivity circuitry 95 to the antenna98 of the LAM/ICM assembly 1 in the form of an RF transmission, throughtransceiver 163 of the communication integrated circuit 65, and to theMCU 87 of the microcontroller 66. Information can also be communicatedin the opposite direction from the MCU 87 of the microcontroller 66,through the transceiver 163 of the communication integrated circuit 65,from antenna 99 in the form of an RF transmission to antenna 98, throughthe internet connectivity circuitry 95, across ethernet connection 97,to the internet 96. The lighting system 94 is typically part of aluminaire (light fixture) that is powered by ordinary 110 VAC wallpower. Symbol 100 represents a source of 110 VAC wall power for theluminaire.

FIG. 14 shows that if the AC-to-DC supply is a constant voltage supply,the MCU 87 can control the FET switch to operate in the FET's linearmode in order to control the magnitude of the constant current 74supplied to the LEDs of the LAM, thereby adjusting the brightness of theLEDs. When operating in this linear mode way, the voltage drop acrossthe FET switch should be about two volts. As explained in further detailbelow, the ICM 3 receives a substantially constant voltage via pins 13and 14 from an AC-to-DC power supply circuit that has a constant voltageoutput, the magnitude of the constant voltage being controllable by azero-to-ten-volt signal received by the AC-to-DC power supply circuit.The voltage that results across pins 13 and 14 when this constantcurrent is being supplied to the LAM/ICM assembly 1 is about 50 volts(or more accurately about 2 volts greater than the forward voltage ofthe LAM). The microcontroller 66 controls the FET switch 67 to fine tunethe amount of current supplied to the LEDs of the LAM by adjusting thevoltage drop across the FET switch to that amount required to achievethe necessary current flow. The voltage drop across FET switch 67 isabout two volts or less depending on the current required, it will benearest zero when maximum current is flowing and nearest 2 volts whenminimum current is flowing. Note that to turn the LEDs off, the FETswitch will be turned off, and the voltage across it will be muchgreater than 2 volts, but since no current is flowing through the FET,no power will be generated within the FET. To prevent excessive powerdissipation by the FET when operating in the linear region, the voltageapplied to the ICM must be within two volts of the forward voltagerequired to illuminate the LED. To accomplish this for a desired LEDbrightness (desired amount of current flow through the LEDs of the LAM),the microcontroller 66 sends a zero to ten voltage dimming controlsignal 89 back to the AC-to-DC power supply circuit 88 via conductor 90,and data terminal 15. The microcontroller 66 uses this control signal 89to increase and to decrease the magnitude of the constant voltage beingoutput by the AC-to-DC power supply circuit 88. The circuit components69, 78, 66 and 65 are powered from a low DC supply voltage such as 3volts DC. A component voltage supply circuit 91 generates this 3 voltsupply voltage from the 50 volts across pins 13 and 14. The 3 voltsupply voltage is supplied onto voltage supply conductor 90. Conductor93 is the ground reference conductor for the component supply voltage.Because only a small amount of power is required to power the circuitryembedded in the ICM, the component voltage supply circuit 91 may be asimple linear voltage regulator.

FIG. 16 is a top-down diagram of another example of a LAM usable withthe ICM. In this example, there are multiple LAM contact pads in eachcorner of the LAM, and there are multiple separately controllablestrings of LED dice. One of these strings includes LED dice 101-110. AnLED drive current can be supplied to this string via LAM contact pad 111and LAM contact pad 112. There are six such separately controllablestrings of the LED dice. The GaN temperature sensing diode is identifiedby reference numeral 32. The LAM contact pads through which the GaNtemperature sensing diode 32 is driven and monitored are LAM contactpads 113 and 114. Reference numeral 34 identifies the rim that retainsthe silicone that covers the LED dice. The silicone is not illustratedin FIG. 16 so that the LED dice disposed under it can be seen in theillustration.

FIG. 17 is a diagram of an LAM/ICM assembly 115 in accordance with athird novel aspect. The LAM/ICM assembly 115 is similar to the LAM/ICMassembly 1 of FIG. 13 explained above, except that: 1) the LAM/ICMassembly 115 of FIG. 17 does not output a 0-10 volt dimming controlsignal, and 2) the LAM/ICM assembly 115 includes a switching DC-to-DCconverter 116. In the example of FIG. 17, the switching DC-to-DCconverter is a buck converter.

FIG. 18 is a more detailed diagram of the buck converter 116. The buckconverter 116 includes a programmable oscillator 117, a switch 118, adiode 119, and inductor 120, and a capacitor 121. Programmableoscillator 117 supplies a rectangular wave digital drive signal 122 tothe switch 118. This drive signal causes the switch to turn on and offin a cyclical fashion. The 50-volt supply voltage from pin 13 isreceived between conductor 123 and conductor 124. From this 50 voltssupply voltage, the buck converter 116 generates and outputs the LEDdrive current 74 at about 48 volts to the LAM via conductor 125.Microcontroller 66 adjusts the frequency and/or duty cycle of signal 112by sending multi-bit digital control information 126 to the oscillator116 across conductors 127. By adjusting the frequency and/or duty cycleof signal 112, the microcontroller 66 controls the magnitude of thenominal output current 74 that the buck converter 116 supplies onconductor 125 to the LEDs of the LAM.

FIG. 19 is a table that sets forth parameters of operation for the buckconverter 116 using 10 MHz nominal switching frequency for the purposeof this explanation. The switching frequency can be substantiallyhigher, as required by the voltages and currents of a particular LAM.

FIG. 20 is a diagram illustrating a first way to drive multiple LEDstrings with multiple buck converters, where the multiple buckconverters are parts of the ICM. In the example of FIG. 20, the buckconverter block 116 of FIG. 17 actually includes multiple buckconverters 128-133. In addition, the LAM includes multiple strings134-139 of LEDs that can be driven independently. Microcontroller 66controls each of the buck converters separately by sending each buckconverter different digital control information across different controllines. The microcontroller 66 controls the frequency and/or duty cycleoutput by each buck converter's programmable oscillator 117 separately.The microcontroller 66 monitors current flow through each string of LEDsone at a time using the same single current sense resistor 77. Providingmultiple buck converters in this way reduces the physical size of theinductors of the buck converters as indicated in the right column ofFIG. 19. Where six LED strings are separately driven, each by a separatebuck converter, the approximate physical size of the inductor of eachbuck converter is 2.5 mm by 2.5 mm by 1.0 mm. This small inductor sizefacilitates encapsulation in a slim ICM profile. While it has beenillustrated that each buck converter could be controlled by individualcontrol signals, it is equally possible to implement the system where asingle oscillator is used to drive multiple buck converter circuitscomposed only of the switch 118, diode 119, inductor 120 and capacitor121, thus further saving on the amount of components required whilekeeping the physical size of the components as small as possible.

FIG. 21 is a diagram illustrating a second way to drive multiple LEDstrings with multiple buck converters, where the multiple buckconverters are parts of the ICM. In this case, each string of LEDs has acorresponding dedicated current sense resistor and FET switch. Currentsense resistor 140 and FET switch 146 are for the first LED string 134.Current sense resistor 141 and FET switch 147 are for the second LEDstring 135. Current sense resistor 145 and FET switch 151 are for thesixth LED string 139.

FIG. 22 is a diagram of a lighting system 152 that includes multipleinstances of the LAM/ICM assembly 115 of FIG. 17 in accordance with thethird novel aspect. Lighting system 152 includes an AC-to-DC powersupply 153, multiple LAM/ICM assemblies 154-159 of the type shown inFIG. 17, and internet connectivity circuitry 95. Bidirectionalcommunication between each of the LAM/ICM assemblies and the internet 96via internet connectivity circuitry 95 is the same as described above inconnection with FIG. 14. Unlike the AC-to-DC power supply 88 of theembodiment of FIG. 14 that outputs a regulated substantially constantcurrent (the magnitude of which is adjustable), the AC-to-DC powersupply 153 of the embodiment of FIG. 22 outputs a substantially constantvoltage that is only roughly regulated. This roughly regulated voltage,in the example of FIG. 22, is 50 volts. This roughly regulated voltageis supplied in parallel to the many LAM/ICM assemblies via conductors161 and 162 as shown. The control of the amount of LED drive currentsupplied to the LEDs of an individual LAM/ICM assembly is controlled bythe switching DC-to-DC converter (for example, a buck converter) withinthe LAM/ICM assembly itself. Each LAM/ICM assembly controls the amountof LED drive current being supplied to its own LEDs. The AC-to-DC powersupply 153 therefore can output a supply voltage that is only roughlyregulated. The AC-to-DC power supply 153 need not receive any 0-10 voltcontrol signal to control its output.

Although an ICM having an embedded DC-to-DC converter is described abovein connection with a specific example in which the switching DC-to-DCconverter embedded in the ICM is a step-down buck converter, this is butone example. In other examples, the embedded switching DC-to-DCconverter is a boost converter whose input voltage is lower than itsoutput voltage. The voltage as received by the embedded boost converteris lower than the voltage (LEDDC) at which the LED array is driven. Inother examples, the embedded switching DC-to-DC converter is acombination boost/buck converter whose incoming input voltage can beeither higher or lower than the converter output voltage. The voltage asreceived by the embedded boost/buck converter may be higher or lowerthan the voltage (LEDDC) at which the LED array is driven. The embeddedswitching DC-to-DC converter may also be a Single-Ended Primary-InductorConverter) SEPIC converter whose output voltage can be less than, equalto, or greater than its input voltage. Any DC-to-DC converter topologywhose characteristics are suitable for the ICM application can beemployed.

Although certain specific embodiments are described above forinstructional purposes, the teachings of this patent document havegeneral applicability and are not limited to the specific embodimentsdescribed above. Accordingly, various modifications, adaptations, andcombinations of various features of the described embodiments can bepracticed without departing from the scope of the invention as set forthin the claims.

What is claimed is:
 1. An assembly comprising: a member; a plurality oflight emitting diodes (LEDs) mounted on the member; an integratedcontrol module (ICM) through which power is supplied to the LEDs,wherein the ICM includes a switching DC-to-DC converter, wherein theswitching DC-to-DC converter receives a substantially constant DCvoltage and supplies a drive current to the LEDs, wherein the ICM has acentral opening, wherein an electrical contact is made between an uppersurface of the member and a bottom surface of the ICM adjacent to thecentral opening through which the switching DC-to-DC converter suppliesthe drive current to the LEDs, and wherein injection molded plasticencapsulates the switching DC-to-DC converter.
 2. The assembly of claim1, wherein the switching DC-to-DC converter is a buck converter.
 3. Theassembly of claim 1, wherein the ICM includes a microcontroller thatmonitors the voltage with which the LEDs are driven.
 4. The assembly ofclaim 3, wherein the microcontroller monitors the drive current flowingthrough the LEDs.
 5. The assembly of claim 3, wherein the ICM includes aFET switch, and wherein the microcontroller controls the FET switch tobe conductive and to turn on the LEDs.
 6. The assembly of claim 1,wherein the ICM includes a microcontroller that supplies a controlsignal to the switching DC-to-DC converter.
 7. The assembly of claim 6,wherein the microcontroller is encapsulated by injection molded plastic.8. The assembly of claim 1, wherein the ICM includes circuitry thatmeasures a temperature of the LEDs, and wherein the circuitry isencapsulated by an amount of injection molded plastic.
 9. An assemblycomprising: a member with a plurality of landing pads disposed on anupper surface of the member; a plurality of light emitting diodes (LEDs)disposed on the upper surface of the member; and an integrated controlmodule (ICM) through which power is supplied to the LEDs, wherein theICM has a central opening with an inside lip, wherein the ICM includes aswitching DC-to-DC converter and a plurality of contact pads, whereinthe contact pads are disposed on a bottom surface of the inside lip,wherein corresponding ones of the landing pads on the upper surface ofthe member are in electrical contact with corresponding ones of contactpads on the bottom surface of the inside lip of the ICM, and wherein theswitching DC-to-DC converter receives a substantially constant DCvoltage and supplies a drive current to the LEDs through the contactpads and the landing pads.
 10. The assembly of claim 9, wherein theswitching DC-to-DC converter is a buck converter.
 11. The assembly ofclaim 9, wherein the LEDs are connected as a first string ofseries-connected LEDs and a second string of series-connected LEDS,wherein the ICM includes a second switching DC-to-DC converter, whereinthe switching DC-to-DC converter supplies the drive current to the firststring of LEDs, and wherein the second switching DC-to-DC convertersupplies a second drive current to the second string of LEDs.
 12. Theassembly of claim 9, wherein the ICM includes circuitry that measures atemperature of the LEDs, and wherein the circuitry is encapsulated by anamount of injection molded plastic.
 13. The assembly of claim 9, whereinthe ICM includes a microcontroller that supplies a control signal to theswitching DC-to-DC converter.
 14. The assembly of claim 13, wherein thedrive current has a magnitude, and wherein the microcontroller controlsthe magnitude of the drive current by adjusting a duty cycle of thecontrol signal.
 15. The assembly of claim 13, wherein an amount ofinjection molded plastic overmolds and encapsulates the microcontrollerand the switching DC-to-DC converter.
 16. The assembly of claim 9,wherein a temperature sensing GaN diode is disposed on the member, andwherein the ICM includes circuitry that monitors the temperature of theLEDs using the temperature sensing GaN diode.
 17. The assembly of claim16, wherein the ICM includes a constant current source that supplies aconstant current to the temperature sensing GaN diode.
 18. An assemblycomprising: a member; a plurality of light emitting diodes (LEDs)mounted on the member; an integrated control module (ICM) through whichpower is supplied to the LEDs, wherein the ICM includes a switchingDC-to-DC converter, wherein the switching DC-to-DC converter receives asubstantially constant DC voltage and supplies a drive current to theLEDs, wherein the LEDs are connected in a first string and a secondstring, wherein each of the first string and the second string is seriesconnected, wherein the ICM includes a second switching DC-to-DCconverter, wherein the switching DC-to-DC converter supplies the drivecurrent to the first string of LEDs, and wherein the second switchingDC-to-DC converter supplies a second drive current to the second stringof LEDs.